What Is a Boiler Flow Switch? This Simple Guide Explains the Basics

What Is a Boiler Flow Switch? This Simple Guide Explains the Basics

Water tube boilers require a constant, minimum water flow rate to operate safely. Manufacturers of finned water tube boilers often utilize a boiler flow switch in addition to or in lieu of the standard low water cutoff. The boiler flow switch is a boiler safety feature or device that prevents the burner from firing in times when the flow of water is interrupted.

If your boiler flow switch has problems, it's imperative to consult with a boiler professional for a solution. Continue reading to learn more about the boiler flow switch and common boiler flow switch problems.

What Is a Flow Switch on a Boiler?

The body of the boiler flow switch should be plumbed into the near boiler system piping. It is often shipped with or pre-piped on the boiler by the manufacturer. This placement ensures that actual boiler water flow will be sensed by the switch and proven.

There are many types of flow switches on the market. Some of the more common types of flow switches seen in current production include differential pressure switches (reading the difference in pressure between two points based on friction loss during flow), paddle switches (a simple spring return switch that is made (closed) when there is flow present and off (open) when there is no flow and magnetic switches. A magnetic switch proves flow as water flows through the device moving a magnet inside of the boiler flow switch body. The magnet keeps the reed switch closed whenever flowing water is present. When the flow of water stops, the magnet moves away from the reed switch, which opens it and breaks the electrical circuit to the burner systems.

Boiler Flow Switch Safety Device

The boiler flow switch is critical to the safety of your boiler. The boiler flow switch prevents burner operation when the system is in bypass (no flow) mode and should be mounted as close to the boiler inlet as possible.

If the burner fires when the system has no flow, it can result in the superheating of water trapped in the water tube which will lead to a failure. The flow switch also prevents the boiler from operating when air is introduced into the system and when the flow volume is insufficient.

Boiler Flow Switch Problems

The most common boiler flow switch problems involve debris clogging the mechanism. Debris and trash in the body of the flow switch can result in the switch contacts being stuck in either the off or on position. In some instances, clogging may prevent the switch operation from being able to completely return to the normal on and/or off position.

Testing the Boiler Flow Switch

It's imperative to conduct regular boiler maintenance, which may include the testing of the flow switch. The flow switch can easily be tested without having to disconnect the electrical leads or dismantling the switch. A simple multimeter is all you need to effectively troubleshoot your flow safety device.

Contact ATI of New York

The experts at Applied Technologies of New York specialize in all things boiler. Whether you need assistance choosing a new fire tube boiler or are looking for ways to reduce NOx to ensure compliance, ATI of New York can guide you in the process.

Contact Applied Technologies of New York today to schedule a consultation.

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